Use a " known good ground " i.e. battery, frame, under hood grounding tab, accessory bracket, etc.... then test all the (+) again, if you are getting power when checking the (+) with a (-) from the harness there is the possibility that a wire is rubbing against another wire. Try this as well get a volt meter and clamp the black wire to the neg. battery and use a jumper and connect the pos. wire to a different ground lug ( back of motor, back of firewall, etc... anywhere there is another ground terminal ) if you are getting (+) from any other grounds, trace the wires back and find where they are rubbing though and touching the bare metal